It is known that, in a storage apparatus such as an RAID (Redundant Array of Inexpensive Disks) apparatus, data recorded in a volatile memory is saved into a nonvolatile memory using power supplied from a capacitor when power supply to a storage apparatus stops (upon power failure).
A capacitor such as an electric double layer capacitor suffers from decrease of the capacitance and increase of the direct current resistance by time-dependent deterioration thereof. Therefore, it is known that power which can be supplied by an electric double layer capacitor decreases by time-dependent deterioration.    [Patent Document 1] International Publication No. 2009/098776    [Patent Document 2] Japanese Laid-Open Patent Publication No. 2005-39873
Generally, an SCU (System Capacitor Unit) that includes an electric double layer capacitor is designed such that power required for saving data recorded in a volatile memory such as a cache memory into a nonvolatile memory is maintained when the product life cycle is exhausted after several years (for example, five years) from its fabrication. In particular, the SCU at an initial stage after the fabrication keeps power that assumes a drop of power, which can be supplied from the electric double layer capacitor, by time-dependent deterioration. Therefore, the SCU keeps surplus power that exceeds power required for saving data recorded in a cache memory into a nonvolatile memory.
Accordingly, since charging time is required also for surplus power when the electric double layer capacitor included in the SCU is charged upon start-up of the storage apparatus, it takes time to start-up the storage apparatus.